Therapeutic use of comfrey is limited because of its toxicity. A limited number of clinical trials show short-term efficacy of topically applied, alkaloid-free comfrey preparations in skin

abrasions and inflammatory conditions. Although not examined in clinical trials, comfrey may possess antifungal and anticancer activity. Comfrey Dosing

Oral

use of comfrey is not supported because of potential hepatotoxicity. Additionally, because externally applied alkaloids are well absorbed and detected in the urine, topical use of comfrey should not exceed an alkaloid exposure of 100 mcg/day. Limited trials have evaluated the efficacy of alkaloid-free preparations for topical use; however, these studies do not report on hepatic laboratory indices of study participants. Contraindications

Comfrey is not recommended for internal use because of the hepatotoxic pyrrolizidine alkaloid content. Patients with hypersensitivity or allergic reactions to the plant should avoid external use. Use is contraindicated during pregnancy and lactation, in infants, and in patients with liver or kidney disease.